The Law of Going to War With Iran

Last week, Israel launched a massive military campaign against Iran aimed (among other possible objectives) at crippling its nascent nuclear program, which Israel has long viewed as an existential threat. It’s a step that Israel has repeatedly threatened but never followed through on, in part due to objections by the United States. Iran has responded in kind, hitting Israel with volleys of drones and missiles that have killed and injured dozens of civilians. Israel is now promising to escalate further in response, through rhetoric that may suggest a shift in its strategic objectives towards regime change, despite public statements to the contrary.

For its part, the Trump administration initially seemed content to sit on the sidelines. Despite his antipathy towards Iran during his first term in office, Trump has spent much of his second trying to secure a negotiated end to their nuclear weapons program along the lines of the Joint Comprehensive Plan of Action that he terminated in 2018—talks that had recently stalled just before Israel began its campaign. He was clearly aware of Israel’s military plans in advance, as evidenced by his administration’s decision to partially evacuate the U.S. Embassy in Baghdad, Iraq, a common target for reprisals by Iran-backed militia groups. But there are no reports that he encouraged or actively supported them. To the contrary, Trump reportedly dissuaded the Israelis from initial plans to target Iran’s Supreme Leader, Ayatollah Ali Khamenei, out of concerns that a regime collapse in Iran—a possible outcome that many supporters suspect is also an objective of the Israeli campaign—could threaten the stability of the entire region.

Yet Trump’s interest in intervening appears to have changed in the past 48 hours. His social media posts on the conflict have turned increasingly bellicose and, as the Iranians have reportedly sought to de-escalate, he has chided them for not negotiating sooner and demanded their unconditional surrender. There is also a strategic case to be made for at least some U.S. involvement, as only the United States has the munitions capable of penetrating and potentially destroying the heavily fortified underground nuclear facility at Fordow, where Iran’s most sensitive nuclear weapons work is believed to take place. Yesterday, it was reported that Trump had approved plans for U.S. military action but not yet authorized it. He later indicated he would make a decision in the next two weeks, giving Iran a window to capitulate or return to the negotiating table.

The possibility that the United States might engage in military action against Iran is not new. During Trump’s first term in office, it was a perennially debated possibility—one that came to partial fruition in the 2020 targeting of Iranian military commander Qassem Soleimani. But it is nonetheless causing an understandable stir. Trump’s own advisers and political allies are sharply split on the issue, with some conventional conservatives—many of whom have long pushed for regime change in Iran—urging Trump to back Israel while key members of his ascendant populist movement oppose it as unnecessary and unwise international interventionism, along the lines of the much-maligned 2003 U.S. military intervention in Iraq. In Congress, meanwhile, the suggestion that the Trump administration would take such a consequential step without meaningfully consulting with—let alone seeking authorization from—Congress has raised constitutional objections, and a bipartisan coalition of legislators has begun taking steps to oppose any U.S. involvement.

At this complex intersection of competing interests, fidelity to the law, both domestic and international, is likely to be just one consideration among many to shape the Trump administration’s response—and, in reality, probably not the most important one. The traditional postures adopted by Congress and the federal courts give the executive branch an immense amount of discretion in interpreting its own legal authority to use military force, which it has done quite permissively. These interpretations are not necessarily correct as a legal matter, but they are what will inform any U.S. military operations unless and until they are superseded by Congress or corrected by the federal courts. As a result, until circumstances compel the other branches of government to adjust their posture—and ongoing efforts in Congress arguably aim to do just that—the executive branch is unlikely to see itself as legally constrained from participating in Israel’s military campaign against Iran, if Trump ultimately opts to do so.

International Law

Compliance with international law is unlikely to be near the top of the list of considerations on Trump’s mind as he weighs intervention in Iran. He and his administration are openly skeptical of the conventional rules-based international system, and—despite some compelling arguments to the contrary—the executive branch (particularly under Republican administrations) has long maintained that the president is not strictly bound by the UN Charter or customary international law. Nor are there legal mechanisms through which other interested parties can readily compel the executive branch to correct its understanding of international law or come back into compliance with it, at least barring specific legislation. That said, during Trump’s first term in office, his office did provide international legal justifications for its military actions—including those targeting Iran—in required reports to the United Nations. Moreover, some plausible international law justification is likely to be important in securing the support (or at least acquiescence) of major allies, something both the Trump administration and Israel are likely to see as useful, though not strictly necessary.

Both customary international law and the UN Charter generally prohibit “the threat or use of force against the territorial integrity or political independence of any state.” Article 51 of the charter, however, makes clear that this restriction is not intended to “impair the inherent right of individual or collective self-defence if an armed attack occurs against a [state.]” While the United States might be able to justify some military actions against Iran on the basis of individual self-defense, the more straightforward legal justification for joining Israel’s military campaign against Iran would be to do so on the basis of collective self-defense, wherein Israel would consent to the United States assisting it in exercising its own individual right of self-defense. Whether this option is available, however, will depend on how the Trump administration views the legality of the military campaign Israel is pursuing.

When it comes to the international law rules regarding the lawfulness of resorting to the use of military force (called the jus ad bellum), most authorities agree that the inherent right of self-defense discussed in the UN Charter extends to threats of imminent armed attacks as well as actual ones. But this is about where the agreement ends, at least where the United States (and Israel) are concerned. As articulated by the International Court of Justice, much of the international community maintains that the right of self-defense applies only to actual or threats of imminent armed attacks that surpass a certain threshold of scale and effects and that, to satisfy requirements for necessity and proportionality under international law, any responsive use of force must be a last resort and narrowly tailored to removing other threats of imminent armed attack. The United States, however, has long dissented from these views. It generally maintains that “any illegal use of force” can trigger the right to self-defense and that assessments of imminence should incorporate a variety of factors, including the “nature and immediacy of the threat” and “whether the anticipated attack is part of a pattern of continuing armed activity.” Moreover, the United States has argued that the use of force is a permissible response so long as a state has explored reasonably available alternatives and that the necessity and proportionality of any military response should be evaluated in line with what is required to address the overall threat posed by a hostile actor. The sum effect of these U.S. arguments is to give states far more leeway in using military force in response to various types of threat. Notably, Israel has generally been closer to the U.S. position on most of these issues than that of the broader international community.

Several international legal scholars have posited reasonable critiques of Israel’s military operations against Iran based on the conventional international law standards regarding the right to self-defense. Among the strongest are the fact that Israel does not appear to be acting in response to any specific threat of an imminent armed attack by Iran in launching its campaign and that the scale of its operations seems unnecessary and out of proportion with what is strictly necessary to address whatever imminent threat Iran might be posing. Yet the U.S. position on these issues would take into account such factors as the possibility of Iran acquiring a nuclear weapon and its long, well-established pattern of hostile rhetoric and action towards Israel (both directly and through proxies). These considerations are likely to make it far easier to justify at least many of Israel's actions.

There is also the real possibility that the United States may not view Israel’s current campaign in isolation. Some legal scholars have argued that Israel and Iran are best understood as having been in an extended armed conflict for the past several years, wherein Israel is acting in self-defense against a much broader pattern of hostilities by Iran through its regional proxies in Gaza, Lebanon, Syria, Yemen, and elsewhere. (Notably, Israel itself seems likely to embrace this framing, as it has hit Iran-affiliated targets in Syria and elsewhere since 2018 in a way that does not clearly correlate with known actual or imminent armed attacks.) In such situations of ongoing hostilities, the United States has argued that the lawfulness of individual military actions need not be weighed in relation to actual or imminent armed attacks, but that the overall armed conflict simply must be necessary and proportional. Again, this is a standard against which it would be far easier to justify Israel’s most recent actions against Iran.

Moreover, there is good reason to believe that the United States would not be alone in this conclusion, despite its idiosyncratic views regarding various aspects of the jus ad bellum. On June 16, the Group of Seven (G7) countries—Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States—issued a joint statement identifying “Iran [a]s the principal source of regional instability and terror[,]” “reiterat[ing] [their] support for the security of Israel[,]” and “affirm[ing] that Israel has a right to defend itself.” This isn’t a full endorsement of the lawfulness of Israel’s military campaign, of course, and the G7 does not necessarily reflect the views of the broader international community. But support from these key allies is likely to bolster the view that Israel’s military campaign is a lawful exercise of the inherent right to self-defense, and that the United States can join that campaign in collective self-defense with Israel at its request.

If and when the United States decides to take this step, it is likely to also posit a right to act on the basis of individual self-defense, as it’s often done in prior similar cases—perhaps in response to Iranian attacks on Israel, where tens of thousands of American citizens reside, or threats against U.S. personnel in Iraq or elsewhere in the region, who are among the most likely to be targeted in reprisals by Iran-backed proxies. As this argument would be secondary, it wouldn’t need to justify the bulk of U.S. military actions. But advancing it would provide a belt-and-suspenders justification and preserve U.S. operational flexibility in the event that it wishes to pursue certain military action to which the Israelis will not consent.

These justifications do not constitute a carte blanche: Specific Israeli and U.S. military operations would have to comply with the rules governing conduct during ongoing armed conflicts (the jus in bello), and the overall conduct of the conflict would have to remain within the outer limits of necessity and proportionality established by the jus ad bellum. Both national militaries generally take the former set of international legal requirements quite seriously, while also embracing highly permissive interpretations that depart from the views of much of the rest of the international community. As for the latter, the United States, at least, has not always seen them as a barrier to major transformative military action, up to and including regime change—as evidenced by the example of the U.S.-led invasion of Iraq in 2003. The United States’s arguments in regard to these aspects of international law are unlikely to be persuasive to much of the international community, limiting their utility from a diplomatic perspective. But as permissive interpretations are well established in executive branch practice, such international legal limits are unlikely to be seen as a barrier to substantial U.S. military engagement, if that is the route the Trump administration wishes to pursue.

Domestic War Powers

Questions of domestic law, meanwhile, are more complicated, but only slightly. How the Constitution allocates authority over the conduct of war has not been firmly resolved by the federal courts, which have often resisted weighing in on such issues. As a result, except where superseded by Congress, the executive branch’s understanding of the law in this area is generally the one that informs U.S. military operations. And as with international law, the executive branch has a long, well-established practice of adopting permissive interpretations of the Constitution that are unlikely to present serious obstacles to at least some U.S. military engagement.

The executive branch has—over frequent objections by legal scholars—long maintained that the president has substantial independent constitutional authority to direct the use of military force against foreign adversaries. While some presidents have claimed a near plenary ability to pursue such action, most recent presidential administrations—including Trump’s during his first term—have generally described this authority as extending, “at least insofar as Congress has not specifically restricted it,” to situations where the president determines (a) military action would “serve sufficiently important national interests” and (b) the “nature, scope, and duration” of anticipated military operations will not “constitute a war requiring prior specific congressional approval under the Declaration of War Clause.” In addition, during his first term, Trump’s Justice Department suggested that the president “has the constitutional authority to take defensive measures to protect U.S. persons” in a manner not subject to these same constraints, but the exact scope of this national self-defense exception remains unclear.

Congress has “specifically restricted” this authority in one regard: As part of the 1973 War Powers Resolution, it requires that, once U.S. armed forces are “introduced … into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances[,]” the president must “terminate” the use of those forces within 60 days (extendable to 90 days in certain circumstances), unless Congress has “enacted a specific authorization for such use[,]” extended the time period by statute, or is physically unable to meet. While some past presidents have suggested that this restriction is unconstitutional, more recent executive branch assessments have generally disagreed, at least outside the context of the national self-defense exception.

The only military action the United States has taken so far in relation to the current Iran-Israel conflict—helping to shoot down Iranian missiles bound for Israel—fits comfortably within this understanding of the president’s authority. Indeed, the Biden administration undertook similar actions in 2024 with little controversy. (A separate question, however, is why neither the Biden nor Trump administration appears to have provided Congress with statutorily required war powers reports within 48 hours of these engagements—a requirement that Congress recently reiterated and expanded upon in 2024 defense authorization legislation. This appears to reflect an executive branch opinion that such reports are not required where military action directly implicates only materiel, not U.S. or foreign personnel.)

Joining Israel’s military campaign against Iran, however, would present a much more difficult set of questions. President Trump might reasonably conclude that such action is consistent with U.S. national interests, at least under the highly deferential standard applied by the executive branch. But Iran remains a major regional military power despite recent setbacks, and engaging it in an extended military campaign naturally presents a risk that the “nature, scope, and duration” of any resulting military operations would escalate substantially. Indeed, Iran has threatened as much in statements hoping to deter Trump from taking such a step.

Whether escalation from a U.S. strike on Iran could lead to a “war requiring prior specific congressional approval under the Declaration of War Clause,” however, is unclear, as the executive branch has never defined where that threshold sits. While leading the Office of Legal Counsel during the Nixon administration, future Chief Justice William Rehnquist described the Korean War as the “high water mark” of executive action without express congressional approval” and posited that the Vietnam War at that stage (in May 1970) would have surpassed this threshold if the Nixon administration did not have the Gulf of Tonkin Resolution and other statutory authorizations to rely upon. That said, subsequent executive branch legal opinions have declined to endorse the constitutionality of U.S. intervention in Korea, suggesting the threshold may be somewhat lower in their eyes. Regardless, as this threshold remains undefined—and any ensuing hostilities with Iran are likely to fall well below the threshold of the Korean War—the Trump administration may well conclude that military action against Iran does not trigger this threshold. Under existing executive branch precedents, the Trump administration could further limit this risk by only using air power, expressly limiting its operations to specific objectives, and not seeking regime change—all factors prior administrations have cited as limiting the risk of escalation.

It is also unclear how readily the Trump administration could sidestep this requirement by justifying such military action as being in U.S. national self-defense. While the United States has targeted Iranian personnel before on a theory of self-defense, it has generally required some nexus with an attack on or imminent threat against U.S. personnel that does not clearly exist here, at least in relation to most of the military targets the United States might pursue. Nor will the administration be able to easily justify its actions as self-defense against the threat of a hostile nuclear Iran (as it might in certain other similar scenarios), as—despite contrary information being provided by some nongovernmental sources—U.S. intelligence has reportedly concluded that Iran is not yet close to developing a nuclear weapon.

Another possible alternative would be for the Trump administration to revert to a broader view of the president’s authority to use military force that concedes no limits from the Declare War Clause or any other source, along the lines most recently articulated (but not relied on) by the George W. Bush administration. In many ways, this would be consistent with Trump’s other extraordinarily broad claims of presidential authority, including in the foreign affairs context. Yet many of Trump’s supporters—including those in his most loyal populist movement—have historically been skeptical of such claims of presidential authority in the war powers context. Relying on a broad claim of presidential war powers to attack Iran—a policy move many of those supporters are already vocally opposing—might trigger a good deal of internal friction within Trump’s coalition, around an issue that carries with it a great deal of political risk for Trump.

Then again, the Trump administration may not rely on the president’s constitutional authority at all. During Trump’s first term, various administration officials floated theories as to why military action against Iran might be authorized by the 2001 and 2002 Authorizations for Use of Military Force (AUMFs), which address post-Sept. 11 attacks and global counterterrorism operations, and U.S. military operations in regard to Iraq, respectively. Those relating to the 2001 AUMF—which authorizes the use of military force against the perpetrators of the Sept. 11 terrorist attacks and provides the legal basis for most U.S. global counterterrorism operations—centered on peripheral Iranian involvement with al-Qaeda in the lead-up to and directly after the attacks, but have rarely been met with anything but skepticism. Theories regarding the 2002 AUMF—which authorizes the use of force “against the continuing threat posed by Iraq[,]” an authorization the executive branch has interpreted widely in subsequent years—have fared only marginally better.

That said, when the Trump administration did ultimately pursue military action against Iranian military commander Soleimani in January 2020, it cited the 2002 Iraq AUMF as one possible legal basis for such action, on the grounds that the statute “has long been read … to authorize the use of force for the related purpose of helping to establish a stable, democratic Iraq and addressing terrorist threats emanating from Iraq” and that “Iran’s past and recent activities in Iraq … indicated that [it] would continue to undermine stability in Iraq and continue to threaten U.S. personnel in Iraq.” Relying on a similar argument to support a broad military campaign against Iran that has no direct nexus to Iraq would represent a dramatic expansion of this theory that few are likely to find persuasive. But if the Trump administration chooses to move forward—and especially if it anticipates military operations lasting long enough to run up against the War Powers Resolution’s 60-to-90 limit, absent statutory authorization—it may be tempted to make such an argument.

Of course, just because the executive branch makes this argument doesn’t mean it’s correct. Legal scholars (including the author) have spilled gallons of ink explaining why reading such extraordinarily broad implied authority to use military force from the president’s constitutionally assigned role as “commander in chief” is hard to square with a text that expressly gives Congress, not the president, the authority to “Declare War[,]” among other issues. But for at least the past half century, federal courts have resisted weighing in on war powers issues and have instead used flexible justiciability and jurisdictional doctrines to avoid reaching the merits. This leaves the executive branch’s legal views—and those of the current president, who is the ultimate decider in the event of disagreement with or among federal agencies—in place as the ones that will inform any U.S. military operation.

That said, there is one scenario in which at least some federal courts—including the Supreme Court—have suggested they may be willing to get involved: where the president is acting contrary to a statute enacted by Congress. And there are signs that such conditions may yet be on the table in regard to military action against Iran.

Opposition in Congress

In the past few days, a bipartisan coalition of legislators have introduced resolutions in both the House and Senate that seek to set limits on Trump’s ability to use military force against Iran. In the Senate, Sen. Tim Kaine (D-Va.) has introduced a joint resolution, S.J. Res. 59, while in the House, Reps. Ro Khanna (D-Calif.) and Thomas Massie (R-Ky.) have introduced a concurrent resolution, H. Con. Res. 38. Each would expressly direct the Trump administration to “terminate the use of United States Armed Forces from hostilities against the Islamic Republic of Iran for any part of its government or military, unless explicitly authorized by a declaration of war or specific authorization for use of military force against Iran[,]” except in cases of “imminent attack.” The House resolution also includes some provisions intended to avoid any disruption in U.S.-Israeli intelligence sharing.

Both resolutions are intended to take advantage of the 1973 War Powers Resolution, albeit in different ways. As originally enacted, the War Powers Resolution included a set of expedited procedures that allowed members of both chambers to introduce concurrent resolutions—a measure requiring only approval by the House and Senate, not signature by the president—directing that U.S. military forces “be removed” from situations of actual or imminent hostilities. The War Powers Resolution in turn directed the president to comply with any such concurrent resolution, essentially providing a mechanism by which Congress could direct the president to end hostilities without having to overcome a possible presidential veto. But in a 1983 decision in INS v. Chadha, the Supreme Court cast the constitutionality of such provisions into serious doubt. A few years later, Congress responded by adding another set of expedited procedures to the War Powers Resolution for joint resolutions, which do require signature (and thus risk a veto) by the president, giving them the full force of law and complying with INS v. Chadha. But for political reasons related to their enactment, the procedures adopted apply in only the Senate, not the House.

There is a question as to whether such resolutions qualify for these expedited procedures, as they address the termination of future participation in hostilities, not the removal of personnel from existing hostilities as the expedited procedure provisions most clearly anticipate. As recently as 2024, the Senate voted to disqualify a joint resolution from the War Powers Resolution’s expedited procedures provisions on the grounds that it did not comply with similar prerequisites—in that case, that the military action being targeted (relief efforts in relation to Gaza) did not constitute “hostilities.” But the joint resolution at issue here is almost identical in wording to a similar resolution the Senate passed through these expedited procedures in 2020, which should help clear major procedural obstacles from its path.

The different procedures available to the two pending resolutions is likely to inform how the relevant resolutions are likely to be used, a pattern that previously played out in debates over military operations relating to Iran and Yemen during Trump’s first term. The concurrent resolution in the House is likely to serve primarily as a vehicle to force House-wide procedural (and potentially substantive) votes to draw attention to the issue and force members to take a public stance, potentially exposing opposition among the president’s supporters. But it’s unlikely to be taken up by the Senate as, even if it were enacted, the executive branch would almost certainly argue that it has no legal effect under INS v. Chadha. The joint resolution, meanwhile, will serve the same purpose in the Senate and, if ultimately adopted, will then become the main legislative vehicle in the House. It won’t benefit from any expedited procedures there, which may make it difficult to get it past the Republican House leadership, which can usually dictate the legislative agenda. That said, the current Republican House majority is narrow and fractious enough that it has occasionally been willing to buck its leadership on such procedural votes, disrupting the speaker’s control of the agenda. Perhaps the debate over the concurrent resolution will succeed in priming the pump enough to make passage a serious possibility.

Of course, even if both chambers pass the joint resolution, this is unlikely to be the end of the road. If intent on military intervention, Trump will almost certainly veto. This will in turn require the support of two-thirds of both chambers to override, a threshold that is likely to be extraordinarily difficult to meet in today’s Congress. During Trump’s first term, this is where similar joint resolutions relating to Yemen and Iran came to their end. The same may prove true here.

A successfully vetoed joint resolution would not have the force of law, but it wouldn’t be a legal nullity. The legal framework through which the Supreme Court usually views a president’s authority to act in situations of shared or uncertain constitutional authority makes it contingent in part on whether it aligns with “the expressed or implied will of Congress[.]” Even a vetoed joint resolution can serve as evidence of congressional disapproval under this standard. (For that matter, so could a concurrent resolution without legal effect, or even resolutions that only pass either the House or the Senate.)

That said, a fully enacted joint resolution—including over any presidential veto—is likely to have far more impact. By expressly directing the president to terminate hostilities against Iran, it puts forward Congress’s preferences quite unequivocally. The president’s authority to act contrary to these preferences is in turn at its “lowest ebb,” meaning he can do so only where he claims “conclusive and preclusive” constitutional authority to do so—an extraordinarily high bar. Perhaps more importantly, this sort of scenario—a clear and unavoidable conflict between the president’s (intended or actual) actions and a statute enacted by Congress—is the sort of scenario in which at least some federal courts have suggested they may well feel obligated to get involved. Hence, even if the Trump administration adopts the view of some prior administrations that the president’s inherent authority to use military force is exclusive to him and thus cannot be limited by Congress, a fully enacted joint resolution might still force the Trump administration to do what no prior administration has had to do in this area: persuade a federal court that its understanding of the Constitution is the correct one.

This joint resolution also won’t be the only bite at the apple. Congress might take the statutory restrictions from a failed joint resolution and later introduce them into omnibus legislation that is more difficult for Trump to veto, such as annual defense authorization or appropriations legislation. This is what it did in the debate over U.S. military involvement in Yemen that raged over much of Trump’s first term in office, ultimately enacting restrictions as part of an annual defense authorization bill Trump could not afford to veto. And it’s how Congress ultimately forced the end of the Vietnam War, over the Nixon administration’s intransigence: by cutting off required funding.

Of course, such measures may come too late if U.S. intervention comes within the next few weeks, especially if it is limited to a discrete set of actions (like targeting the facility at Fordow) that does not require a longer term military campaign. Much the same is true for any judicial intervention that might follow such restrictions. But the debate Congress is poised to have over the resolutions in the days to come may yet help to demonstrate just how much opposition there is to U.S. military action against Iran, including among Trump’s own supporters—and that may be enough to shape the path forward that the Trump administration ultimately chooses to pursue.

Implications for U.S. Intervention

For many, the conclusion that neither domestic nor international law is likely to keep the president from single-handedly making a decision as consequential as going to war with Iran may well be a disturbing one. It’s also difficult to square with the intent of the framers, who clearly sought to restrain the United States from engaging in foreign wars too readily. But this legal reality—that “one person decides,” as Jack Goldsmith once described it—is the one Americans have been living within for much of the past century.

This does not mean that relevant legal structures, even as interpreted by the executive branch, view all potential forms of military engagement equally. Applicable domestic and international legal frameworks both favor narrow, more discrete forms of military engagement that specifically target Iran’s nuclear program or other serious threats to the United States or Israel. Past executive branch precedents also make certain types of military operations easier to square with its vision of the president’s constitutional authority—specifically, those that use air power instead of ground troops, are focused on narrow objectives (especially where tied to national self-defense), and do not seek to hold or control territory. And the Trump administration faces an incentive to avoid extended military campaigns, which will raise the question of the War Powers Resolution’s 60- to 90-day cut-off and create more opportunities for congressional (or even judicial) pushback. In short, the conventional legal views of the executive branch make it easier to accommodate military action like a limited air strike on a facility like Fordow. They are much more skeptical (though not necessarily prohibitive) of the sort of broader military campaign that may be required to force an outcome like regime change, at least absent some statutory authorization.

Of course, the Trump administration may not feel constrained by the conventional views of the executive branch. While Trump mostly stuck by conventional executive branch views during his first term in office, he has aggressively pushed beyond them in a number of different contexts during his second, including in regard to his authority over foreign affairs. Hence, Trump may ultimately prove willing to assert the authority to take extraordinary actions in ways that other presidents would not. And if he does, it’s not clear that there are currently legal mechanisms in place to stop him.

This state of affairs is not, however, an immutable aspect of our constitutional system. Congress could enact stricter statutory limitations on the executive branch and, while the executive branch may contest their constitutionality and seek to act beyond them, doing so may finally force the federal courts to intervene and weigh in on the proper allocation of war powers under the Constitution. In this fight, there is ample reason to think that Congress will ultimately win. But the deliberative pace of the institutions and procedures that could lead to such an outcome leaves the executive branch with ample room to take the initiative in the meantime.

This article builds on work associated with the Congressional Study Group on Foreign Relations and National Security and was made possible in part by a grant from the Carnegie Corporation of New York. The statements made and views expressed are solely the responsibility of the author.